Most electronic devices or modules include both through-hole components and surface mounted components attached to a printed circuit board. The components typically are attached to the circuit board by solder or an electrically conductive adhesive. Soldering may occur manually or by other techniques, including reflow soldering and wave soldering.
When manufacturing large quantities of electronic circuits, solder material usually is applied to electrically conductive pads of the circuit board during one or more solder paste printing process steps. The printing process occurs by applying the solder paste through an appropriately configured stencil or mask. The stencil is configured to have apertures formed through the stencil at locations corresponding to the conductive pads of the circuit board where solder is to be deposited. The stencil is positioned over the circuit board and the solder paste is applied to the circuit board in a known manner.
For example, U.S. Pat. No. 4,739,919 discloses a mask for shielding surface mounted components during a wave-soldering process. In this way, surface mounted components are protected while the leads of selected through-hole circuit components may be soldered to the circuit board.
U.S. Pat. No. 5,593,080 to Teshimi et al. discloses a mask of varying thickness for depositing varying amounts of solder onto differently sized pads of a circuit board.
U.S. Pat. No. 5,617,990 to Thompson, Sr., discloses a shield for use in a wave-soldering process. The shield has solder flow openings formed through the shield for applying solder to the circuit board. Recesses also are formed in the shield to cover and protect selected electronic components during the soldering process.